1. Technical Field
The present disclosure relates to a method of manufacturing a thin film transistor (TFT) substrate, and more particularly, to a method of manufacturing a TFT substrate that reduces a rugged surface of an organic layer overlapping with a storage electrode.
2. Discussion of the Related Art
In a liquid crystal display (LCD) apparatus, a plurality of pixel electrodes perform operations to display an image on a display area comprised of a set of unit pixels. The plurality of pixel electrodes are formed at a plurality of unit pixels, respectively. The pixel electrodes are driven by a signal applied thereto through wire. The wire includes a gate line and a data line which cross each other to define a unit pixel area. A scan signal is applied to the gate line to control a signal applied to a pixel electrode through the data line.
Each pixel includes a liquid crystal capacitor which changes the light transmission characteristics of a liquid crystal according to a voltage applied thereto, thereby adjusting the amount of transmitted light. The voltage applied to the liquid crystal capacitor should be maintained during a frame, but it is difficult to maintain a constant voltage only with the liquid crystal capacitor. To maintain each pixel's ability to sustain the voltage, a storage capacitor is connected to the liquid crystal capacitor in parallel in each pixel.
When a data wire and a semiconductor layer in a TFT substrate are patterned using a single mask, the semiconductor layer, except for a channel portion, substantially underlies and overlaps with the data wire. Accordingly, the semiconductor layer exists under a data electric conductor forming a storage capacitor. The semiconductor layer included in the storage capacitor, like a MOS capacitor, causes the change in capacitance of the storage capacitor according to a voltage applied to the storage capacitor. The change in capacitance results in flickering on a display unit of an LCD apparatus. To prevent the change in capacitance, the semiconductor layer overlapping with the storage electrode is etched and removed.
After a passivation layer and an organic layer are deposited, an opening is formed in the organic layer. A pixel electrode is ultimately formed in the opening, whereby the pixel electrode overlaps a storage electrode to form a storage capacitor. Upon formation of the opening, a portion of the organic layer overlapping with the storage electrode is left behind using a slit mask. At this time, the organic layer may have a rugged surface. As a result of the rugged surface, the passivation layer and a gate insulating layer under the opening are etched during subsequent processing, resulting in exposure of the storage electrode and a possible short-circuit of a pixel electrode. In addition, the rugged surface causes a difference of capacitance of the storage capacitor according to a position on a storage capacitor, resulting in flickering in the LCD apparatus.